Method of improving gasoline quality



Nov. 25, 19 58 METHOD R. W. SAGE ET AL OF IMPROVING GASOLINE QUALITY Filed Feb. 29, 1956 3 KHz/d Richard W Sage Cliffon H. Jones Inventors Attorney United vStates Patent 2,861,946 METHOD OF 'INIPRQVING GASOLINE QUALITY Richard W. Sage, Fanwood, N. J., and, Clifton H. Jones, Palembang, South Sumatra, Indonesia, assignors to Esso Research and Engineering Company, a corporation of Delaware Application February 29, 1956, Serial No. 568,659 Claims. (Cl. 208-144) The present invention relates to a method of improving gasoline. More particularly, the present invention relates to improving the stability of gasoline constituents obtained by coking, catalytic cracking and thermal cracking of hydrocarbons to reduce the di-olefinicity of said gasoline constituents and thus to improve the engine cleanliness characteristics of such constituents.

It is known that gasoline which contains unsaturates, particularly, di-olefins, tends to form gummy material in storage and in combustion in an internal combustion engine and thus the use of such gasoline as a motor fuel or an aviation gasoline results in deposits in the engine, resulting, of course, in a lowering of the efficiency of such engine in operation. It has heretofore been the practice to add various materials to an unstable gasoline to prevent such gum formation. For example, vegetable lecithin has previously been proposed as such an additive to an unstable gasoline to prevent polymerization or oxidation of the olefins therein, and thus prevent or retard gum formation. It has also been proposed previously to hydrofine a gasoline to increase its stability by treating the unstable gasoline with a hydrogen-containing gas, preferably, in the presence of a catalyst, such as cobalt molybdate carried on a spacing agent which may be active alumina, silica, activated carbon and the like. The improved stability when hydrofining is achieved by saturation of both monoand di-olefinic components of the gasoline. The processes for gasoline treating for stability improvement currently known to the art have a generally common disadvantage, namely, the removal or saturation by hydrogen addition of significant quantities of mono-olefins as well as the undesired di-olefins. Since mono-olefins are of good octane quality, the resulting gasoline is seriously degraded in octane quality although of satisfactory stability.

In brief compass, the present invention relates to the treatment of an unstable gasoline or appreciable quantities of di-olefins, with a catalyst such as platinum or palladium or any good hydrogenation-dehydrogenation catalyst, which catalyst has previously been treated with a hydrogen-containing gas in order that the said catalyst adsorb or occlude hydrogen, whereby the occluded hydrogen chemically reacts with the di-olefins of the unstable gasoline subjected to the treatment, converting them principally to mono-olefins or saturates without, however, saturating with hydrogen the mono-olefins, which may be originally contained in the said gasoline to any substantial degree. As a result of treating according naphtha containing to this invention, the undesirable di-olefins are removed,

' I mono-olefins are not significantly affected and essentially no octane debit is incurred. This desirable treatment is possible under the conditions of this invention since hydrogen for saturation is available only at the catalytic surface and the morereactive components of the gasoline (i. e., the di-olefins) are more strongly attracted to the catalytic surface and, therefore, receive the hydrogen before substantial quantities of mono-olefins can migrate to the catalyst surface and react.

The main object of the present invention is to remove the di-olefins selectively from a gasoline containing such di-olefins, without substantially afiecting the mono-olefins which are desirable components of said gasoline, in a manner which is cheaper and more eflicient than the previously proposed methods for accomplishing this result.

Another object of the present invention is to improve the stability of a gasoline containing substantial quantities of olefins, such as a gasoline obtained from a so-called fluid coking operation, a catalytically cracked gasoline, a thermally cracked gasoline, or other similar gasoline products, by treating such gasolines at elevated temperatures with a catalyst previously treated with a hydrogencontaining gas, whereby the said catalyst receives adsorbed or occluded hydrogen, said hydrogen being transferred to the gasoline being treated during the treating period.

Another object of the present invention is to condition the hydrogenation-dehydrogenation catalyst with a gas containing hydrogen in substantial quantities, whereby the catalyst adsorbs hydrogen and is thereby adapted to release such hydrogen in a chemical reaction to hydrogenate the di-olefins contained in a normally liquid hydrocarbon.

Other and further objects of the present invention will appear from the following more detailed description and claims.

In the accompanying drawing there is depicted, diagrammatically, an apparatus in which a preferred modification of the present invention may be carried into effect.

Referring in detail to the drawing, 1 represents a vessel containing a fixed bed of catalyst C. This catalyst may be in the form of pills, pellets, granules, shaped bodies or any known conventional form; and 2 represents a second vessel also containing a fixed bed of catalyst C in the same physical form and chemical composition as the catalyst C in vessel 1. As Will appear presently, these vessels are operated in parallel.

In the description immediately following, it will be assumed that catalyst bed C in vessel 1 contains catalyst previously treated with a hydrogen-containing gas such as a tail gas from a catalytic reforming unit. A gasoline containing substantial quantities of olefins such as a gasoline obtained by subjecting a relatively high boiling petroleum oil fraction to a fluid coking operation, enters the present system through line 3 and is charged to a heating means 4 which may be an ordinary furnace in which the feed passes through a fired coil 5 or a conventional heat exchanger wherein it is heated to reaction temperatures and thereafter charged via line 6 to the top of vessel 1. The preheated feed passes downwardly through the bed of catalyst C and the occluded hydrogen in the catalyst chemically reacts with the di-olefins under consulfide on the alumina.

pressure, the higher figure ditions more fully set forth in a specific example hereinafter. Conditions are maintained in vessel 1 so that the di-olefins in the feed are substantially hydrogenated to convert them to the corresponding mono-olefin, while at the same time the mono-olefins present in the original feed are not hydrogenated to any substantial degree. No hydrogen, other than occluded by the catalyst is reacted. The treated product is withdrawn from treater 1, through line 8, thence passed through a condenser 9 where it is cooled to a temperature of about 100 thence withdrawn from cooler 9 via line and delivered to a storage drum 11.

There comes a time, of course, at which the hydrogen occluded in the catalyst C in reactor 1 is exhausted, and at this time the flow of oil to vessel 1 is discontinued by manipulation of valve V, and the oil in line 6 is charged to vessel 2 by manipulation of valve V in line 6a, the catalyst C having meanwhile been treated with a hydrogen-containing gas in a manner presently to be explained. The treated oil is withdrawn from vessel 2, via line 12, charged to line 8 and thereafter treated in a manner previously explained in connection with the product treatment of the material in line 8.

In order to restore the hydrogen which has been used up by treatment of product in vessel 1, the said hydrogen may be replenished by treatment with a gas containing hydrogen, say, the tail gas from catalytic cracking or catalytic reforming units. This gas enters the present system through line 13, thence is passed through heating means 14, thence withdrawn from 14 via line 15 and charged at a point near the bottom of vessel 1. It is to be understood that the hydrogen-containing gas may be passed either upfiow or downfiow over the catalyst.

Under conditions more fully set forth hereinafter, the catalyst receives hydrogen from the hydrogen-containing gas by adsorption or occlusion as the gas passes in contact upwardly through the bed of catalyst C. The hydrogen depleted treating gas is rejected from the vessel 1 overhead via line 16 and this gas may be used as a fuel or it may be treated according to any desired method.

In like manner, the catalyst in vessel 2 may be treated with preheated hydrogen-containing gas at a time when the hydrogen content of the catalyst is depleted by first discontinuing the oil flow by manipulation of the valve in 6a and the manipulation of the valves in lines 15 and 15a to direct flow of such hydrogen-containing gas to vessel 2.

In order to explain the invention more fully, there is set forth below a specific example illustrating a preferred modification of the invention.

A platinum-containing catalyst was prepared by impregnating activealumina with platinum by immersing the saidalumina in a solution of chloroplatinic acid. The platinum was removed from the impregnating solution by treatingwith hydrogen sulfide to precipitate platinum The resulting paste was subsequently calcined in air at 950 F. for three hours and thereafter treated with hydrogen at 900 F. at atmospheric pressure until the platinum sulfide was converted to the metal. The catalyst was then cooled and held until the hereinafter described experiments were carried out. At the start of the experiment the catalyst was heated to 900 F. from 250 F. at the rate of 70 'F./hr. in at atmosphere of nitrogen gas and thereafter cooled to 600 F.

In preliminary tests it was found that a platinum catalyst occluded or adsorbed 4-8 cc. of hydrogen per gram of catalyst (standard conditions) by treatment with a gas, of'low hydrogen concentration, at low and higher pressures, respectively, the lower figure at atmospheric (8 cc.) at the 200 p. s. i. g. employed in the'hydrogen adsorption-step.

Thereafter a naphtha feed having an inspection set forthin-below table was treated under theconditions set "forth in' the table with the results "setforth:

Operating conditions Cycles 1-10 2 Cycles 11-20 2 Time of Run Date Hour Date Hour Start 4/22 1259 4/23 0057 Finish- 4/22 2312 4/23 0853 Catalyst 0.5 wt. percent Pt on 99.5 wt.

percent A Catalyst Charge, Gms 368 368 Heat t reat ment of catalyst before H,

rea 2 Temperature Increased from 250 F. to 900 F.

70 F./hr. Pressure Atmospheric... Atmospheric. Atmosphere Nitrogen... Nitrogen.

Catalyst Precondition Step: I12 Rate, V./V./Hr. Temperature, F..

Pressure, p. s. i. g 200. Length of Cycle (Mim). 10. Catalyst Purge Step:

N Rate, V./V./Hr. Temperature, F. Pressure, p. s. i. g..-...

Feed Treat Step:

Oil Feed Rate, W./Hr./W Oil Feed Rate, ml./hr.- Temperature, F Pressure, p. s. i. g Length of Cycle (Min.) Product Recovery, Wt. percent...

Volumcs of gas conditions/volume of catalyst/hr. Catalyst case held 480 cc. of catalyst (368 gms.).

2 Each cycle represents 30 minutes of operation as follows: 10 min. catalyst preconditioning with hydrogen, 10 min. catalyst purging with nitrogen, 10 min. feed treating.

Results Product Sample Feed Cycles Cycles Best Re- 1-10 2 11-20 2 suits Temperature, F.- 603 550 520 Pressure, p. s. i. g 200 200 200 Catalyst 0.5 wt. percent Pt on 99.5

Gravity, API

Wt. percent alumina.

36. 0 36. 5 36. 7 36. 2 Research Octane No. 94. 3 93. 2 04. 0 94. 3 Peroxide No. 2. 3 Trace 0.1 0. 1 Bromine No., Cg./Gm. 20. 7 11.1 18. 8 25 Lamp Sulfur, Wt./percent 0. 32 0.13 0.21 0.29 Diene No., Mgm. Br/Gm. 0. 71 0. 23 0.25 0.27 DFDF 20.3 0.5 1.0 1.5

deposit factor (DFDF) test. This test identifies the presence of reactive diolefins by causing them to react with diazonium fluoroborate followed by measurement of the optical density of the sample and correction for boiling range. These reactive diolefins have been shown to be major contributors to the formation of engine deposits in gasolines. It can be seen that the treatment effected in both periods of operation essentially eliminated these reactive components of the feed stock. It is important in substantiating the claims of this invention to observe the effect of the treatment on the bromine number of the feed. Treatment at 603 F. reduced the bromine number by 15.6 units from 26.7 to 11.1 cg./gm. while at a 550 F. treating temperature, the bromine number reduction was only 7.9 cg./ gm. Best results on this particular feed are obtained at 520 P. where the bromine number change was essentially nil (26.7 vs. 25 og./gm.'). This degree of bromine number reduction would be expected from elimination of diolefins.

In further reference to the foregoing example, it is pointed out that after treating the catalyst with a hydrogen-containing gas to cause adsorption of the hydrogen by the catalyst, and prior to charging the oil to the reaction zone, the said reaction zone was purged with nitrogen in order to remove all hydrogen not adsorbed by the catalyst, thus establishing that it was the hydrogen adsorbed by the catalyst which caused hydrogenation of the diolefins in the naphtha feed and not residual hydrogen in the catalyst bed voids.

To recapitulate briefly, the present invention relates to a method of removing di-olefins from motor fuel or aviation gasoline without significantly affecting the desirable mono-olefins by causing the oil containing di-olefins to contact a catalyst containing adsorbed or occluded hydrogen. Any good hydrogenation catalyst may be used to adsorb the hydrogen including platinum, palladium, nickel and others well known in the art. The pretreatment of the catalyst with a hydrogen-containing gas for hydrogen adsorption may be efiected at pressures of from to 1500 p. s. i. g., and at temperatures of from 100 to 1200 F. It is also pointed out that the hydrogen-containing gas utilized for pretreating the platinum catalyst may be either pure hydrogen or a gas such as the tail gas from a catalytic oil cracking process, the tail gas from a hydroforming process or from any other source in which the gas contains at least -10% mol percent hydrogen. In connection with hydroforming carried out in the presence of a fluidized bed of catalyst or where the process is carried out in the presence of a fixed bed, and further, wherein the catalyst is periodically regenerated, it is conventional practice to strip the spent catalyst with steam to remove volatile hydrocarbon therefrom. If the spent catalyst is stripped with tail gas from the hydroforming process, the catalyst in the case of platinum will adsorb or occlude hydrogen originally contained in said tail gas, and thus this stripped catalyst containing adsorbed hydrogen may be utilized in the present process to stabilize aviation gasoline or motor fuel by the hydrogenation of di-olefins contained in these gasolines.

Numerous modifications of the invention may be made by those who are familiar with this art.

What is claimed is:

l. The method of stabilizing a cracked gasoline, containing substantial amounts of mono-olefins and di-olefins, which comprises contacting, a platinum group metal catalyst carried on an adsorptive support with a gas contain ing hydrogen at a temperature in the range of to 1200 F. and a pressure in the range of 0 to 1500 p. s. i. g., whereby the said platinum metal group catalyst selectively adsorbs hydrogen, thereafter contacting the said gaso line containing olefins with the said catalyst in the absence of extraneous hydrogen at elevated temperatures, whereby the major portion of the said di-olefins are hydrogenated by the hydrogen held by the catalyst without substantially hydrogenating the mono-olefins and thereafter recovering a gasoline of improved stability.

2. The method set forth in claim 1 in which the gasoline is contacted with the catalyst containing adsorbed hydrogen, under conditions such that the said di-olefins are converted to the corresponding mono-olefins.

3. The method set forth in claim 1 in which the gas containing hydrogen is obtained from a product recovery system of a hydroforming process.

4. The method set forth in claim 1 in which the gas containing hydrogen is obtained from the product recovery system of a catalytic cracking process.

5. The method set forth in claim 1 in which the platinum group metal is platinum metal.

References Cited in the file of this patent UNITED STATES PATENTS 2,419,323 Meinert et al Apr. 22, 1947 2,542,970 Jones Feb. 27, 1951 2,694,671 Baumgarten et a1 Nov. 16, 1954 

1. THE METHOD OF STABILIZING A CRACKED GASOLINE, CONTAINING SUBSTANTIAL AMOUNTS OF MONO-OLEFINS AND DI-OLEFINS, WHICH COMPRISES CONTACTING, A PLATINUM GROUP METAL CATALYST CARRIED ON AN ADSORPTIVE SUPPORT WITH A GAS CONTAIN1200*F. AND A PRESSURE IN THE RANGE OF 0 TO 1500 P.S.I.G., WHEREBY THE SAID PLATINUM METAL GROUP CATALYST SELECTIVELY ABSORBS HYDROGEN, THERAFTER CONTACTING THE SAID GASOLINE CONTAINING OLEFINS WITH THE SAID CATALYST IN THE ABSENCE OF EXTRANEOUS HYDROGEN AT ELEVATED TEMPERATURES, WHEREBY THE MAJOR PORTION OF THE SAID DI-OLEFINS ARE HYDROGENATED BY THE HYDROGEN HELD BY THE CATALYST WITHOUT SUBSTANTIALLY HYDROGENATING THE MONO-OLEFINS AND THEREAFTER RECOVERING A GASOLINE OF IMPROVED STABILITY. 